Simulating an engine-turned finish

[charlie8575]

Title pretty much says it all.

I'm thinking BMF, followed by a light burnishing with 5-aught steel wool to knock the shine down, followed by one of those little fibreglass brush thingies you use for knocking rust out of scratches on 1:1 cars prior to applying touch-up paint.

Anyone else have any other ideas?

Charlie Larkin

[Ace-Garageguy]

I've seen it done in some of the larger scales using one of the slightly gritty pencil-shaped typewriter (remember those?) erasers with the tip turned down to an almost-point, chucked up in a low-speed Dremel. Perfectly convincing.

Edited March 4, 2014 by Ace-Garageguy

[sjordan2]

Handmade patterns at small scale would be a hit-or-miss proposition, and there'd probably be too much texture to be realistic. You might try playing with the exposures and scale on this stuff, then making clear decals to put on BMF or similar material.

[Art Anderson]

Title pretty much says it all.

I'm thinking BMF, followed by a light burnishing with 5-aught steel wool to knock the shine down, followed by one of those little fibreglass brush thingies you use for knocking rust out of scratches on 1:1 cars prior to applying touch-up paint.

Anyone else have any other ideas?

Charlie Larkin

I've done "engine turning" (also used to be called "damascening") on model cars before, but way back in my "Indy Car" building days (My last Indy car model was under construction right at 30 years ago as of today!), and as Bill Engwer states, those old-fashioned "pencil" typewriter erasers were the only thing I found that would work. Those erasers had, instead of graphite "lead", a rod of fairly soft eraser rubber which was impregnated with fine abrasive grit.

The trouble was, however, that the rubber "tip" I could get when running that eraser in a pencil sharpener could not easily be sharpened down to less than perhaps .060", and then not precisely. I wound up "hardening" the rubber with old-fashioned thin viscosity CA glue, then carefully shaping the tip with an Xacto knife and VERY tediously making a flat, hopefully true end to it. The sections (I cut off 1/2" lengths of the eraser "pencils", then drilled out the broad end for inserting lengths of 1/8" music wire (spring steel), inserted that into the broad end, securing that with CA glue. These "tools" (I made over a dozen of them for each of the three Watson roadsters and a nearly total scratchbuild of a Watson USAC dirt track Champ car) were chucked into my variable speed Dremel, which in turn was clamped into a rather imprecise Dremel drill press.

The material I used for the firewalls and instrument panels was thin aluminum sheet--actually used "Offset Printing" masters from our church, where my Mom was the secretary--used a small offset printer to publish the church newsletter and Sunday worship bulletins, so this was "free" material. After a bit of practice, I was able to get a reasonably accurate, even set of turnings, but they were larger than exact scale, as most real engine turning is done with mandrels ranging from 1/2" (.020" in 1/25 scale) up to perhaps 1 1/2" or .060" in our scale. The smallest I was able to achieve this way was perhaps .080" or thereabouts, which was a bit large, but the effect was good enough to help my Dirt Champ Car win the "Best Scratchbuilt" award at the IPMS Nationals at Indianapolis in 1985.

The problem with trying this on BMF is simply the thin, delicate nature of Bare Metal Foil. Of course, it goes without saying that probably the sort of typing eraser I was able to find back then (and that was problematic, given the advent of "White-Out" liquid eraser and the white "correction tape" that followed very quickly--and of course today, who even uses an old-fashioned typewriter with a woven silk ribbon?

I have used steel wool to "dress" BMF, back when I did a number of scale aircraft models, and wanted to replicate a factory fresh all-metal airplane or two, but that was laying a straight "brushed" pattern across the foil, to suggest the rolling marks found on brand new aircraft aluminum of years past, but I would wonder if steel wool could be used on a mandrel anywhere near small enough to create a damascened pattern on BMF without simply tearing the foil apart on the sheet. As for those round tools with short glass fibers, I cannot imagine finding any of those nearly small enough to do realistic engine-turned patterns on a 1/25 scale model, and the problem of simply tearing up the foil would still be a hurdle to overcome.

At NNLE a couple of years ago, some aftermarket outfit was selling decal sets for the Revell Kurtis midgets, some of which had bright gold numbers having a swirled, almost prismatic look to them that was quite realistic. Those were done to replicate the once-very popular gold leaf graphics and numbers on a lot of racecars, which had it's swirled, almost damascened appearance achieved by the signpainter using ordinary cotton balls to lightly scuff the actual gold leaf in rotary, swirled patterns, but those swirls were a good 2-3" in diameter back then.

Art

[Skip]

As Art referred to engine turning on Gold Leaf it's now done with velveteen over a dowel rod. Most signwriters I know are good enough they can freehand it! You might be able to do this with BMF, not sure it's soft enough though.

[sjordan2]

What would your specific applications be? Dash? Firewall? What kit or kits, at what scale? Any visual examples of what you're going for?

[shucky]

I thought Scott Colmer did a tutorial on this many years ago? He achieved that exact look in scale using a pencil eraser with a punched out piece of high grit sand paper glued to the tip of the eraser. He then hand turned each of the "circles" in the desired pattern (like the picture in Skip's post above). I believe this tutorial was in MCM a bunch of years ago. The look he achieved quite simply by doing this by hand was dead-on. I believe he did this on thin gauge aluminum sheet, not BMF.

[lonewolf01]

what about using a .025 rod and valve grinding paste

[Ace-Garageguy]

what about using a .025 rod and valve grinding paste

Worth trying, but I'd think that wiping the highly abrasive paste off of the part would make undesired scratches.

The beauty of the old eraser trick is that there's no residue other than possibly a little dry dust that will blow off.

[Psychographic]

Cotton balls are used to burnish gold leaf, real velvet is used to turn it.

Edited March 13, 2014 by Psychographic